Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.36	5.852%	$117.8768	$117.88	$117.90	$117.90
Purchase #2	$123.38	3.812%	$128.0832	$128.08	$128.10	$128.10
Purchase #3	$250.80	5.181%	$263.7939	$263.79	$263.80	$263.80
Purchase #4	$66.27	5.453%	$69.8837	$69.88	$69.90	$69.90
Purchase #5	$88.83	7.695%	$95.6655	$95.67	$95.65	$95.70
Purchase #6	$38.58	9.844%	$42.3778	$42.38	$42.40	$42.40
Purchase #7	$215.92	10.514%	$238.6218	$238.62	$238.60	$238.60
7 purchase totals =	$895.14		$956.3027	$956.30	$956.35	$956.40